CN110922351A

CN110922351A - Separation and purification method of aromatic diimide

Info

Publication number: CN110922351A
Application number: CN201911296991.1A
Authority: CN
Inventors: 李旭峰; 张鑫; 陈海波
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2020-03-27
Anticipated expiration: 2039-12-17
Also published as: CN110922351B

Abstract

The invention discloses a separation and purification method of aromatic diimide, which comprises the steps of dissolving crude aromatic diimide synthesized by nucleophilic reaction in a high-boiling-point polar aprotic solvent, adding a reducing agent for reaction, cooling for crystallization, filtering at low temperature, adding the obtained product into the high-boiling-point polar aprotic solvent again, and performing temperature reduction and recrystallization to obtain purified aromatic diimide. The separation and purification process described is useful for producing aromatic diimides, advantageously allowing the production of aromatic diimides having undetectable levels of residual dihydroxy aromatic compounds. The aromatic diimide obtained by the invention is used for preparing products obtained by polyetherimide, has the advantages of low color number, excellent mechanical property and the like, and can meet new requirements of customers for products used for various applications.

Description

Separation and purification method of aromatic diimide

Technical Field

The invention discloses a preparation process of aromatic diimide, in particular to a process for refining aromatic diimide by using a separation and purification method such as recrystallization.

Background

Polyetherimides are a class of high performance polymers that can be processed to make molded articles, fibers, films, foams, and the like. Polyetherimides also have high strength, toughness, heat resistance, modulus, and broad chemical resistance, and are therefore widely used in a variety of industries such as automotive, telecommunications, aerospace, electrical/electronics, transportation, and healthcare. Polyetherimides have shown versatility in a variety of manufacturing processes, proving useful in technologies including injection molding, extrusion, and thermoforming to produce a variety of articles.

However, some polyetherimides do not meet the stringent purity requirements required for certain applications, for example, polyetherimides may need to have very low contaminant levels, or processability and product properties are adversely affected. Common resin contaminants can be organic or inorganic in nature. Organic contaminants are primarily lower molecular weight species, including residual phenolic monomers or derivatives thereof. In addition to affecting polymer properties, residual monomers may also be of concern in view of emerging regulatory factors.

Thus, there remains a continuing need for improved methods for producing high quality polyetherimides, particularly polyetherimides having undetected levels of residual phenolic monomers or derivatives thereof.

In polyetherimide manufacture, the nucleophilic reaction by the dialkali metal salt of a dihydroxy aromatic compound with a reactive substituted phthalimide is the core reaction of the overall manufacturing process. Since the reaction is an equilibrium reaction, there will inevitably be a small amount of reactants remaining in the product as well as the corresponding monosubstituted salt of the dihydroxy aromatic compound. These residues will significantly affect the color of the product and the color of the final polyetherimide. Because the structure of the residual impurities is close to that of the product, the purification difficulty of the product is very high. Usually, water and/or ethanol washing purification methods are used, and the purity of the obtained product can only reach 95%, and the color of the product is still yellow. The better purification method is not reported.

Therefore, it is still very urgent to develop a high-efficiency separation and purification method for the above nucleophilic reaction products.

Disclosure of Invention

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a separation and purification process suitable for nucleophilic reaction synthesis of aromatic diimide, which can provide a residual dihydroxy aromatic compound having an undetected level and a selectively reduced content of quinone-based substances having an important influence on the color of the product, by a treatment method such as recrystallization and reduction using a polar aprotic solvent having a high boiling point. The process has less product loss in the separation process, the yield is over 90 percent, the product is white, and the purity is over 99.95 percent.

The invention provides a method for separating and purifying aromatic diimide, which comprises the following steps:

1) reacting a dialkali metal salt of a dihydroxy aromatic compound with a reactive substituted phthalimide under conditions effective to form a product mixture, and then washing and drying the product mixture of the reaction to obtain a crude product;

2) dissolving the crude product obtained in the step 1) in a high-boiling-point polar aprotic solvent, heating to 80-140 ℃, adding a reducing agent, reacting at 100-140 ℃, preferably 120-130 ℃ for 1-6 h, preferably 2-4 h, then cooling to-20-10 ℃, preferably-20-0 ℃, performing heat preservation crystallization, and filtering at low temperature to obtain a filter cake;

3) adding the filter cake obtained in the step 2) into a high-boiling-point polar aprotic solvent, heating to 100-140 ℃, dissolving, filtering while hot, cooling the filtrate to-20-10 ℃, preferably-20-0 ℃, performing heat preservation and recrystallization, filtering at low temperature, and sequentially washing, washing with ethanol and drying the filter cake to obtain the purified aromatic diimide.

In the method, in the steps 2) and 3), the high-boiling-point polar aprotic solvent is at least one selected from Dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc), and preferably any two of the solvents are compounded in a volume ratio of 1:1. The high boiling polar aprotic solvents described in step 2) and step 3) may be the same or different. It is generally accepted that DMSO, DMF and DMAc, due to their solubility which is too high, are used in recrystallization in low yields (typically not exceeding 70%) and are not industrially feasible. The inventors found that the solubility of DMSO, DMF and DMAc for aromatic diimides is significantly reduced at low temperatures, the single pass yield exceeds 97%, and the purification effect on the product is excellent.

In the method, in the step 2), the temperature is reduced, wherein the temperature reduction rate is 0.2-3 ℃/min, and preferably 0.5-1 ℃/min; the cooling time is 0.5-10 h, preferably 4-8 h;

the heat preservation crystallization time is 1-5 h, preferably 2-4 h; the temperature is-20 to 10 ℃ below zero, preferably-20 to 0 ℃.

In the cooling and crystallization process, the stirring speed is in the range of 30-200 rpm, preferably 80-150 rpm.

In the step 2), the low-temperature filtration is carried out, wherein the temperature is-20-10 ℃, preferably-20-0 ℃, and the filtration pressure is 0.2-0.4 MPa (gauge pressure), preferably 0.2-0.3 MPa (gauge pressure).

In step 2), the reducing agent is selected from at least one of metal powder, potassium iodide, sulfite, and the like, preferably at least one of zinc powder, iron powder, and sulfite. The potassium iodide and the aluminum powder can be complexed with a system to form colloid after reducing quinone substances, so that the separation is difficult. Therefore, the more preferable choices are zinc powder, iron powder and sulfite, wherein the zinc powder and the iron powder are preferably particles of 50-300 meshes.

The addition amount of the reducing agent is 1-2 wt% of the mass of the crude product.

In the step 2), the crude product obtained in the step 1) is introduced into a mixer containing a high-boiling-point polar aprotic solvent for heating and dissolving, and preferably, the mass ratio of the high-boiling-point polar aprotic solvent to the crude product is controlled within the range of 1-3: 1. In some embodiments, the method comprises adding the high-boiling polar aprotic solvent into a mixer, keeping the temperature between 80 and 120 ℃, adding the crude product into the mixer under mechanical stirring, and dissolving the crude product, wherein the rotation speed of a stirring paddle is 100 to 500rpm, and stirring and mixing for about 0.5 to 1 hour until the product is completely dissolved.

In the step 3), the temperature is reduced by the program at a rate of 0.2-3 ℃/min, preferably in 3 stages, and is firstly reduced to 60-80 ℃ at a rate of 0.2-0.5 ℃/min, then reduced to 30-40 ℃ at a rate of 1-3 ℃/min, and finally reduced to-20-10 ℃ at a rate of 0.2-0.3 ℃/min.

The heat preservation recrystallization time is 2-8 h, preferably 4-6 h; the temperature is-20 to 10 ℃ below zero, preferably-20 to 0 ℃.

In the cooling and recrystallization processes, the stirring speed is in the range of 30-200 rpm, preferably 50-80 rpm.

In the step 3), the hot filtration refers to filtration after dissolution at 100-140 ℃, and residual reducing agents and oxidation products can be separated and removed through hot filtration. The low-temperature filtration is carried out at the temperature of-20-10 ℃, preferably-10-0 ℃, and the filtration pressure is 0.1-0.5 MPa (gauge pressure), preferably 0.2-0.3 MPa (gauge pressure).

In the step 3), the dosage of the high-boiling-point polar aprotic solvent is calculated by taking the crude product added in the step 2) as a reference, and the mass ratio of the high-boiling-point polar aprotic solvent to the crude product is controlled within the range of 4-1: 1.

The process of the present invention, step 1), the product mixture (i.e., crude) comprises a dialkali metal salt of a dihydroxy aromatic compound, the corresponding dihydroxy aromatic compound, at least one of the corresponding monosubstituted salts of the dihydroxy aromatic compound, or a combination comprising at least one of the foregoing, and an aromatic diimide.

In steps 1) and 3), the washing, drying and the like are conventional methods, any known method can be adopted without specific limitation, and in some embodiments, the specific method adopted in the washing and drying in step 1) is to firstly add ethanol for mixing, vacuum-filter, then wash with water and dry. The step 3) comprises water washing and ethanol washing, preferably 2 times of water washing at normal temperature and 1 time of ethanol washing.

The method takes the crude product in the step 1) as a reference, and the yield of the aromatic diimide after recrystallization in the steps 2) and 3) is over 90 percent, and the preferred scheme can reach over 97 percent; the total yield of the aromatic diimide prepared by adopting the separation and purification method of the invention is more than 90 percent calculated by the initial raw material nitrophthalimide of the reaction.

The aromatic diimide product prepared by the separation and purification of the invention is white and has a color number less than 10. Which contains residual dihydroxy aromatic compound impurities (e.g., bisphenol a) in an amount less than 500ppm, more preferably less than 100ppm, and most preferably less than 1 ppm. The content of quinone compounds in the impurities is less than 1 ppm.

The residual dihydroxy aromatic compound impurity generally refers to a dialkali metal salt of a dihydroxy aromatic compound, a corresponding monosubstituted salt of the dihydroxy aromatic compound, or a combination comprising at least one of the foregoing.

The process for preparing an aromatic diimide according to the present invention, step 1), which is a process for the preparation of a dialkali metal salt of a dihydroxy aromatic compound by reaction with a reactive substituted phthalimide, can be carried out under any conditions generally known in the art with the aim of efficiently forming a product mixture.

In some embodiments, the product mixture comprises a dialkali metal salt of a dihydroxy aromatic compound, a corresponding monosubstituted salt of the dihydroxy aromatic compound, and an aromatic diimide. Wherein the content of the dialkali metal salt of the dihydroxy aromatic compound as an impurity, the corresponding dihydroxy aromatic compound and the corresponding mono-substituted salt of the dihydroxy aromatic compound is usually 2 to 5 wt%, and the content of the quinone compound in the impurity is usually 1500 to 3000 ppm.

In some embodiments, the product mixture comprises residual reactive substituted phthalimide, a hydrolyzed derivative thereof, or both.

The dialkali metal salt of the dihydroxy aromatic compound has a structure represented by formula (1)

M+-O-Z-O-+M (1)

Wherein M is selected from an alkali metal ion, such as lithium, sodium, potassium, or a combination comprising at least one of the foregoing. In some embodiments, M is sodium. Z is an aromatic C6-24 monocyclic or polycyclic moiety optionally substituted with 1 to 6C 1-8 alkyl groups, 1 to 8 halogen atoms, or a combination comprising at least one of the foregoing. Exemplary Z groups can be groups comprising the structure shown in formula (2)

Wherein, Ra and

or a monovalent C1-6 alkyl group, Ra and Rb may be the same or different; p and q are each independently an integer from 0 to 4; c is 0 to 4; and Xa is a bridging group connecting the hydroxy-substituted aromatic groups, wherein the bridging group and the hydroxy substituent of each C6 arylene group are located ortho, meta, or para (particularly para) to each other on the C6 arylene group.

The bridging group Xa may be a single bond, -O-, -S-, -S (O) -, -S (O)2-, -C (O) -, or a C1-18 organic bridging group. The C1-18 organic bridging group can be cyclic or acyclic, aromatic or non-aromatic, and can also contain heteroatoms such as halogens, oxygen, nitrogen, sulfur, silicon, or phosphorus. The C1-18 organic bridging group can be arranged such that the C6 arylene groups attached thereto are each attached to a common alkylidene carbon or to different carbons of the C1-18 organic bridging group. Specifically, the Z group is a divalent group having a structure represented by the formula (2a)

Wherein Q is selected from the group consisting of-O-, -S-, -C (O) -, -SO₂-, -SO-or-p (Ra) (═ O) -, where Ra may be C1-8 alkyl or C6-12 aryl, or-CyH 2 y-where y is an integer from 1 to 5, or a halogenated derivative thereof. Exemplary dihydroxyaromatic compounds that may be derived from the Z group include, but are not limited to, 2-bis (2-hydroxyphenyl) propane, 2,4 ' -dihydroxydiphenylmethane, bis (2-hydroxyphenyl) methane, 2-bis- (4-hydroxyphenyl) propane ("bisphenol A" or "BPA"), 1-bis- (4-hydroxyphenyl) ethane, 1-bis- (4-hydroxyphenyl) propane, 2-bis- (4-hydroxyphenyl) pentane, 3-bis- (4-hydroxyphenyl) pentane, 4 ' -dihydroxybiphenyl, 4 ' -dihydroxy-3, 3,5,5 ' -tetramethylbiphenyl, 2,4 ' -dihydroxybenzophenone, bisphenol A, 4,4 '-dihydroxydiphenyl sulfone, 2, 4' -dihydroxydiphenyl sulfone, 4 '-dihydroxydiphenyl sulfoxide, 4' -dihydroxydiphenyl sulfide, hydroquinone, resorcinol, 3, 4-dihydroxydiphenylmethane, 4 '-dihydroxybenzophenone, 4' -dihydroxydiphenyl ether, or the like, or a combination comprising at least one of the foregoing. In some embodiments, the Z group is preferably 2,2- (4-phenylene) isopropylidene (i.e., the dihydroxy aromatic compound derived from a dialkali metal salt is 2, 2-bis (4-hydroxyphenyl) propane (bisphenol A).

The reactive substituted phthalimide has a structure represented by formula (3)

Wherein X is fluorine, chlorine, bromine, iodine, nitro, or a combination comprising at least one of the foregoing, and R1 is a C1-13 monovalent organic group. In some embodiments, X is nitro. In some embodiments, R1 is a C1-13 monovalent alkyl group, preferably a C1-4 monovalent alkyl group, such as methyl. In some embodiments, X is nitro and R1 is methyl. In some embodiments, the reactive substituted phthalimide comprises 4-nitro-N-methylphthalimide, 3-nitro-N-methylphthalimide, or a combination comprising at least one of the foregoing.

The product mixture may also include a corresponding monosubstituted salt of a dihydroxy aromatic compound having the structure shown in formula (4)

Wherein M, Z and R1 are as defined above for formulas (1-3). In some embodiments, M is sodium, Z is 2,2- (4-phenylene) isopropylidene, and R1 is methyl.

In some embodiments, the reaction of the dialkali metal salt of the dihydroxy aromatic compound with the reactive substituted phthalimide is conducted in the presence of one or both of a solvent and a catalyst. Thus, in addition to comprising at least one of a dialkali metal salt, a corresponding dihydroxy aromatic compound, a corresponding monosubstituted salt of the dihydroxy aromatic compound, or a combination comprising at least one of the foregoing, the product mixture may further comprise a solvent. Any non-polar organic solvent that does not react with the reactants during the aromatic diimide formation can be used for the reaction, with high boiling polar aprotic solvents being preferred. Suitable solvents include, but are not limited to, DMF, DMSO, DMAc, or the like, or a combination comprising at least one of the foregoing. In some embodiments, the solvent preferably comprises DMF.

In some embodiments, the product mixture further comprises a phase transfer catalyst. In some embodiments, the phase transfer catalyst is a hexaalkylguanidinium salt or a tetraalkylammonium salt. For example, the phase transfer catalyst can be hexaethylguanidinium chloride, tetraethylammonium bromide, tetraethylammonium acetate, tetrabutylammonium bromide, and the like. Mixtures of catalysts may also be used. In some embodiments, the phase transfer catalyst is preferably a hexaalkylguanidinium salt, such as hexaethylguanidinium chloride.

The dialkali metal salt of the dihydroxy aromatic compound and the reactive substituted phthalimide may be reacted under any suitable reaction conditions generally known in the art. For example, the reaction may be carried out at a temperature of 25 to 180 ℃, preferably 85 to 125 ℃, more preferably 100 to 125 ℃. The reaction is preferably carried out in the presence of a solvent, and in some embodiments, the product mixture may have a solids content of 20 to 50 wt%, where the term "solids content" is defined as the weight of the dialkali metal salt of the dihydroxy aromatic compound and the reactive substituted phthalimide relative to the total weight of the product mixture. The reaction may also be carried out in the presence of a phase transfer catalyst. The phase transfer catalyst may be present in an amount of 0.3 to 10 mol% based on the moles of the dialkali metal salt of the dihydroxy aromatic compound. In some embodiments, 0.7 to 1.2 mol% of a phase transfer catalyst may be used, preferably wherein the phase transfer catalyst is a hexaalkylguanidinium salt, more preferably wherein the phase transfer catalyst is hexaethylguanidinium chloride. In some embodiments, 1.8 to 2.2 mol%, preferably 2 mol% of a phase transfer catalyst may be used, for example when the phase transfer catalyst is a tetraalkylammonium salt, preferably tetrabutylammonium bromide. The molar ratio of the dialkali metal salt of the dihydroxy aromatic compound to the substituted phthalimide may be 1:1.7 to 2.3, preferably 1: 2.

the product mixture comprises an aromatic diimide having the structure shown in formula (5)

Wherein Z and R1 are as defined above for formulas (1-4). The divalent linkage of the-O-Z-O-group is located at the 3,3 ', 3, 4', 4,3 'or 4, 4' position of the phenyl ring of the phthalimide. In some embodiments, Z is 2,2- (4-phenylene) isopropylidene and R1 is methyl.

In some embodiments, the aromatic diimide comprises 4,4 '-bisphenol-a-bis-N-methylphthalimide, 3' -bisphenol-a-bis-N-methylphthalimide, or a combination comprising at least one of the foregoing.

In some embodiments, the product mixture may further comprise an inorganic alkali metal salt. In some embodiments, the inorganic alkali metal salt may be derived from a reactive substituted phthalimide. For example, when the reactive substituted phthalimide comprises a nitro-substituted N- (C1-13 alkyl) phthalimide (e.g., 4-nitro-N-methylphthalimide, 3-nitro-N-methylphthalimide, or a combination comprising at least one of the foregoing), the product mixture may further comprise an alkali metal nitrite (e.g., sodium nitrite). For example, when the reactive substituted phthalimide comprises a chloro-substituted N- (C1-13 alkyl) phthalimide (e.g., 4-chloro-N-methylphthalimide, 3-chloro-N-methylphthalimide, or a combination comprising at least one of the foregoing), the product mixture can further comprise an alkali metal chloride (e.g., sodium chloride). In some embodiments, when the inorganic alkali metal salt is present, it is present as a solid precipitate in the product mixture (i.e., the inorganic alkali metal salt is insoluble in the product mixture).

The separation and purification process of the present invention advantageously allows the production of aromatic diimides having low color number, low residual dihydroxy aromatic compounds (e.g., bisphenol a), meeting the new requirements of customers for a variety of articles of manufacture. The aromatic imides produced according to the methods of the invention can be used to produce the corresponding polyetherimides. Polyetherimides having undetectable levels of residual dihydroxy aromatic compound, especially selectively reduced levels of quinones that have a significant effect on product color, may be advantageously used in the manufacture of articles for use in a variety of applications, particularly applications where extremely high color requirements are placed upon or where extremely high requirements are placed upon dihydroxy aromatic compound residue in view of customer requirements or regulatory considerations. In particular, it finds application in applications including food service, medical, lighting, lenses, scopes, windows, enclosures, security barriers, cookware, medical devices, trays, panels, handles, helmets, animal cages, electrical connectors, enclosures for electrical devices, engine parts, automotive engine parts, lighting sockets and reflectors, motor parts, power distribution equipment, communication equipment, computers, and the like. Accordingly, their article categories may include, for example, hollow fibers, hollow tubes, hollow tube fibers, wherein the fiber walls have small openings of various pore sizes that provide permeable membrane fibers, other shaped permeable membranes having various pore sizes, solid fibers, sheets, films, multi-layer sheets, multi-layer films, molded parts, extruded profiles, coated parts, foams, windows, luggage racks, wall panels, chair parts, lighting panels, diffusers, lamp housings, partitions, lenses, skylights, lighting, reflectors, piping, cable trays, conduits, pipes, cable ties, wire coatings, electrical connectors, air handling devices, ventilation equipment, shutters, insulation, boxes, storage containers, doors, hinges, handles, sinks, mirror housings, mirrors, toilet seats, hangers, coat hooks, racks, ladders, handrails, steps, carts, trays, Cookware, food service equipment, medical equipment, data transfer equipment, powders, composites, communications equipment, dashboards, and the like.

During the development of an aromatic diimide manufacturing process, the inventors have discovered that an aromatic diimide product can be purified by a specific recrystallization process using a high boiling polar aprotic solvent, which recrystallization technique can provide residual dihydroxy aromatic compounds with undetectable levels. It is inevitable that trace impurities remain in the product, which affects not only the color of the product, but also the color of downstream polyetherimide products. And the residual impurity structure is close to the product, so that the separation difficulty is extremely high. In response to this problem, the inventors have conducted intensive studies on the composition of the product mixture and found that the quinone species formed after oxidation of the incompletely reacted monosubstituted salt has a considerable influence on the color of the product. Because the structure of the formed quinone substances is very close to that of the product, the separation and purification by recrystallization and the like are difficult. After a large amount of experimental exploration, we find that the quinone substances are reduced into mono-substituted salts by using reducing agents (such as zinc powder, iron powder and sulfite), and then the mono-substituted salts can be dissolved in a high-boiling polar aprotic solvent for removal, so that the content of the quinone substances which have important influence on the color of the product is selectively reduced.

The present invention provides a substantial improvement in the process for producing aromatic imides and polyetherimides. The use of the separation and purification methods described for the production of aromatic diimides advantageously allows the production of aromatic diimides having undetectable levels of residual dihydroxy aromatic compounds (e.g., bisphenol a). The aromatic diimide obtained by the invention is used for preparing products obtained by polyetherimide, has the advantages of low color number, excellent mechanical property and the like, and can meet new requirements of customers for products used for various applications.

Detailed Description

In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The separation and purification process for the preparation of aromatic diimides is further illustrated only by the following non-limiting examples.

First, embodiment main raw material and reagent source information:

hexaethylguanidinium chloride: purchased from alatin, purity 98%;

bisphenol a disodium salt: self-making;

nitrophthalimide: self-made, with the purity of 99%;

zinc powder: purchased from alatin, 100 mesh;

iron powder: purchased from alatin, 100 mesh;

sodium sulfite: purchased from alatin, 99% pure;

aluminum powder: purchased from alatin, 100 mesh;

DMAc: purchased from Jiangsu Honghui chemical industry, with the purity of 99 percent;

other common raw materials are commercially available unless otherwise specified.

Second, the main testing method and the instrument used in the embodiment

1. The purity was tested by model 1290Infinity II ultra high performance liquid chromatograph from agilent using acetonitrile as mobile phase.

2. The color numbers were tested by a CR-30 colorimeter from Chimaphila principality, Inc. at 25 ℃.

3. Quinone content: tested according to GB/T23675-2009.

Example 1

Aromatic diimides are prepared according to the disclosed process: reacting disodium salt of bisphenol A (100g, 367 mmol) with a solution of nitrophthalimide comprising 3-nitrophthalimide and 4-nitrophthalimide (151.47g, 735mmol) in DMF (640 mL) in the presence of hexaethylguanidinium chloride (HEGCl; 1.0g,3.7mmol) as a phase transfer catalyst, stirring under nitrogen, reacting at 120 ℃ for 2 hours, cooling the product mixture to room temperature, mixing with 1000mL of ethanol under mechanical stirring at 500rpm, vacuum filtering, water washing and drying to obtain a crude aromatic diimide comprising 4,4 '-bisphenol-A-bis-N-methylphthalimide, 3, 4' -bisphenol-A-bis-N-methylphthalimide and 3, the impurity content of the residual dialkali metal salt, the corresponding dihydroxy aromatic compound and the corresponding mono-substituted salt of the dihydroxy aromatic compound contained in the crude product of the solid mixture of 3' -bisphenol-A-bis-N-methylphthalimide was 2.4% by weight, and the quinone compound content was 1500 ppm.

Example 2

The crude product prepared in example 1 was isolated and purified:

250g of the crude product prepared in example 1 are dissolved in 800mL of DMAc, heated to 120 ℃ and then 2.5g of zinc powder are added, mixed with stirring at 500rpm for about 1h until the product is completely dissolved, and then reacted at 120 ℃ for 3h, after which the solution is transferred to a cooling crystallizer. The temperature is reduced to 0 ℃ according to the program at the speed of 0.5 ℃/min and the rotating speed of 100rpm, and the temperature is kept for 4h for crystallization. And (3) carrying out filter pressing at the temperature of 0 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining a filter cake.

The filter cake was redissolved in 500mL of DMAc and DMSO (1:1 by volume) at 110 ℃ and filtered hot, and the filtrate was then crystallized by cooling by programmed cooling to 0 ℃ with mechanical stirring at 50 rpm. The temperature reduction procedure is divided into 3 sections, and the temperature is reduced to 80 ℃ at the speed of 0.5 ℃/min, then reduced to 40 ℃ at the speed of 2 ℃/min, and finally reduced to 0 ℃ at the speed of 0.3 ℃/min. Held at 0 ℃ for 4 h. And (3) carrying out filter pressing at the temperature of 0 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining a filter cake. And washing the filter cake with 500mL of water for 2 times and 500mL of ethanol for 1 time at 25 ℃, performing vacuum filtration, and drying to obtain the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and recrystallization is 94.1 percent calculated by taking the aromatic diimide in the crude product as the reference; the total yield of the method is 91.4 percent by adopting the separation and purification method of the invention and calculating by using the initial raw material of the reaction, namely the nitrophthalimide. The aromatic diimide product had a color number of 5 and a purity of 99.9997% and contained 5ppm of impurities including residual dialkali metal salts, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.5ppm) of quinone compounds.

Example 3

The crude product prepared in example 1 was isolated and purified:

250g of the crude product are dissolved in 600mL of DMAc and DMSO (1:1 by volume), heated to 100 ℃ and 3.5g of zinc powder are added, mixed with stirring at 500rpm for about 1h until the product is completely dissolved, reacted at 130 ℃ for 2h and the solution is then transferred to a cooling crystallizer. The temperature is reduced to-10 ℃ according to the program at the speed of 1 ℃/min and the rotating speed of 150rpm, and the temperature is preserved for 3h for crystallization. Carrying out filter pressing at the temperature of minus 10 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining a filter cake.

The filter cake was redissolved in 500mL of DMAc and DMF (1:1 by volume) at 120 ℃ and filtered hot, and the filtrate was then crystallized by cooling by programmed cooling to-10 ℃ with mechanical stirring at 50 rpm. The temperature reduction procedure is divided into 3 sections, and the temperature is reduced to 60 ℃ at the speed of 0.2 ℃/min, then to 30 ℃ at the speed of 3 ℃/min, and finally to-10 ℃ at the speed of 0.2 ℃/min. The temperature was kept at-10 ℃ for 6 h. Carrying out filter pressing at-10 ℃ and filtering pressure of 0.3MPa to obtain a filter cake. And washing the filter cake with 500mL of water for 2 times and 500mL of ethanol for 1 time at 25 ℃, performing vacuum filtration, and drying to obtain the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and recrystallization is 96.4 percent calculated by taking the aromatic diimide in the crude product as the reference; the total yield of the method is 92.8 percent by the separation and purification method based on the reaction initial raw material of the nitrophthalimide. The aromatic diimide product had a color number of 5 and a purity of 99.9993%, and contained 7ppm of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.6ppm) of quinone compound.

Example 4

The crude product prepared in example 1 was isolated and purified:

250g of the crude product is dissolved in 600mL of DMSO, heated to 120 ℃ and then 5g of zinc powder are added, stirred and mixed at 500rpm for about 1h until the product is completely dissolved, then reacted at 110 ℃ for 5.5h, and the solution is transferred to a cooling crystallizer. And (3) carrying out programmed cooling to-15 ℃ at the rotating speed of 150rpm according to the speed of 2 ℃/min, and carrying out heat preservation for 2h for crystallization. Carrying out filter pressing at the temperature of minus 10 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining a filter cake.

The filter cake was redissolved in 500mL of DMAc and DMF (1:1 by volume) at 120 ℃ and filtered hot, and the filtrate was then crystallized by cooling by programmed cooling to-10 ℃ with mechanical stirring at 50 rpm. The temperature reduction procedure is divided into 3 sections, and the temperature is reduced to 70 ℃ at the speed of 0.3 ℃/min, then reduced to 35 ℃ at the speed of 2 ℃/min, and finally reduced to-10 ℃ at the speed of 0.3 ℃/min. The temperature was kept at-10 ℃ for 8 h. Carrying out filter pressing at the temperature of minus 10 ℃, wherein the filter pressure is 0.3MPa gauge pressure, and obtaining a filter cake. And washing the filter cake with 500mL of water for 2 times and 500mL of ethanol for 1 time at 25 ℃, performing vacuum filtration, and drying to obtain the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and recrystallization is 97.2 percent calculated by taking the aromatic diimide in the crude product as the reference; the total yield of the method is 93.5 percent by adopting the separation and purification method of the invention and calculating by using the initial raw material of the reaction, namely the nitrophthalimide. The aromatic diimide product had a color number of 8 and a purity of 99.9993%, and contained 10ppm of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.6ppm) of quinone compound.

Example 5

The crude product prepared in example 1 was isolated and purified: the only difference from example 2 is that the reducing agent was replaced with 2.5g of iron powder.

The yield of the aromatic diimide after separation, purification and recrystallization is 94.7 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to prepare the aromatic diimide product with the total yield of 91.9 percent by calculating the initial reaction raw material of the nitrophthalimide.

The aromatic diimide product had a color number of 4 and a purity of 99.9998% and contained 3ppm of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.5ppm) of quinone compound.

Example 6

The crude product prepared in example 1 was isolated and purified: the only difference from example 2 was that the reducing agent was replaced with 2.5g of sodium sulfite.

The yield of the aromatic diimide after separation, purification and recrystallization is 93.6 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to prepare the aromatic diimide product with the total yield of 91.1 percent by calculating the initial reaction raw material of the nitrophthalimide.

The aromatic diimide product had a color number of 8 and a purity of 99.9993%, and contained 11ppm of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.6ppm) of quinone compound.

Example 7

The crude product prepared in example 1 was isolated and purified: the difference from example 2 is only that the reducing agent was replaced with 2.5g of aluminum powder, which was affected by colloidal clogging, and the filtration rate of the reaction system after reduction was slow.

The yield of the aromatic diimide after separation, purification and recrystallization is 93.2 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to prepare the aromatic diimide product with the total yield of 90.5 percent by calculating the initial reaction raw material of the nitrophthalimide.

The aromatic diimide product had a color number of 10 and a purity of 99.9985% and contained less than 95ppm of impurities including residual dialkali metal salts, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.8ppm) of quinone compounds.

Example 8:

the crude product prepared in example 1 was isolated and purified:

250g of the crude product prepared in example 1 are dissolved in 800mL (about 727g) of DMAc, heated to 120 ℃ and 2.5g of zinc powder are added, mixed with stirring at 500rpm for about 1h until the product is completely dissolved, and then reacted at 120 ℃ for 3h, after which the solution is transferred to a cooling crystallizer. The temperature is reduced to 25 ℃ according to the program at the speed of 0.5 ℃/min and the rotating speed of 100rpm, and the temperature is kept for 4h for crystallization. And (3) carrying out filter pressing at 25 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and thus obtaining a filter cake.

The filter cake was redissolved in 500mL of DMAc and DMSO (1:1 by volume) at 110 ℃ and filtered hot, and the filtrate was then crystallized by cooling by programmed cooling to 0 ℃ with mechanical stirring at 50 rpm. The temperature reduction procedure is divided into 3 sections, and the temperature is reduced to 80 ℃ at the speed of 0.5 ℃/min, then reduced to 40 ℃ at the speed of 2 ℃/min, and finally reduced to 25 ℃ at the speed of 0.3 ℃/min. Held at 25 ℃ for 4 h. And (3) carrying out filter pressing at 25 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and thus obtaining a filter cake. And washing the filter cake with 500mL of water for 2 times and 500mL of ethanol for 1 time at 25 ℃, performing vacuum filtration, and drying to obtain the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and recrystallization is 90.8 percent calculated by taking the aromatic diimide in the crude product as the reference; the total yield of the method is 90.0 percent by the initial raw material nitrophthalimide. The aromatic diimide product had a color number of 10 and a purity of 99.8327%, and contained 400ppm of impurities including residual dialkali metal salts, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and less than 1ppm (about 0.9ppm) of quinone compounds.

Comparative example 1

Separation and purification: the difference from example 2 is that the reduction treatment was omitted and the reducing agent zinc powder was not added.

The yield of the aromatic diimide after separation, purification and recrystallization is 92.4 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to calculate the initial raw material nitrophthalimide of the reaction, so as to obtain the product of the aromatic diimide with the total yield of 89.3%. The aromatic diimide product had a color number of 120 and a purity of 97.6847%, and contained 2.3 wt% of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and 1300ppm of quinone compound.

Comparative example 2

Separation and purification: 250g of the crude product prepared in example 1 are dissolved in 600mL of DMSO, heated to 120 ℃ and 5g of zinc powder are added, mixed with stirring at 500rpm for about 1h until the product is completely dissolved, and then reacted at 110 ℃ for 5.5h, after which the solution is transferred to a cooling crystallizer. And (3) carrying out programmed cooling to-15 ℃ at the rotating speed of 150rpm according to the speed of 2 ℃/min, and carrying out heat preservation for 2h for crystallization. And (3) carrying out filter pressing at the temperature of minus 10 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and crystallization is 96.3 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to calculate the initial raw material nitrophthalimide of the reaction, so as to obtain the product of the aromatic diimide with the total yield of 91.5%. The aromatic diimide product had a color number of 60 and a purity of 98.1997%, and contained 1.8 wt% of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound, and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and 500ppm of quinone compound.

Comparative example 3

Separation and purification: 250g of the crude product prepared in example 1 are dissolved in 500mL of DMAc and DMSO (1:1 by volume) at 110 ℃ and filtered while hot, and the filtrate is then crystallized by cooling by programmed cooling to 0 ℃ with mechanical stirring at 50 rpm. The temperature reduction procedure is divided into 3 sections, and the temperature is reduced to 80 ℃ at the speed of 0.5 ℃/min, then reduced to 40 ℃ at the speed of 2 ℃/min, and finally reduced to 0 ℃ at the speed of 0.3 ℃/min. Held at 0 ℃ for 4 h. And (3) carrying out filter pressing at the temperature of 0 ℃, wherein the filter pressure is 0.2MPa gauge pressure, and obtaining a filter cake. And washing the filter cake with 500mL of water for 2 times and 500mL of ethanol for 1 time at 25 ℃, performing vacuum filtration, and drying to obtain the aromatic diimide product.

The yield of the aromatic diimide after separation, purification and recrystallization is 96.5 percent calculated by taking the aromatic diimide in the crude product as the reference; the separation and purification method of the invention is adopted to calculate the initial raw material nitrophthalimide of the reaction, so as to obtain the product of the aromatic diimide with the total yield of 91.8%. The aromatic diimide product had a color number of 80 and a purity of 98.8024%, and contained 1.2 wt% of impurities including residual dialkali metal salt, the corresponding dihydroxy aromatic compound and the corresponding monosubstituted salt of the dihydroxy aromatic compound, and 480ppm of quinone compound.

Claims

1. A method for separating and purifying aromatic diimide is characterized by comprising the following steps:

2. The method according to claim 1, wherein in steps 2) and 3), the high-boiling polar aprotic solvent is selected from at least one of dimethylformamide, dimethyl sulfoxide and dimethylacetamide, preferably any two of the solvents are compounded in a volume ratio of 1: 1; the high-boiling polar aprotic solvents described in step 2) and step 3) may be the same or different;

in the step 2), the mass ratio of the high-boiling-point polar aprotic solvent to the crude product is 1-3: 1;

in the step 3), the dosage of the high-boiling-point polar aprotic solvent is calculated by taking the crude product added in the step 2) as a reference, and the mass ratio of the high-boiling-point polar aprotic solvent to the crude product is 4-1: 1.

3. The method according to claim 1 or 2, wherein in step 2), the temperature is reduced at a rate of 0.2 to 3 ℃/min, preferably 0.5 to 1 ℃/min; the cooling time is 0.5-10 h, preferably 4-8 h.

4. The method according to any one of claims 1 to 3, wherein in step 2), the incubation crystallization time is 1 to 5 hours, preferably 2 to 4 hours;

in the cooling and crystallization process, the stirring speed is 30-200 rpm, preferably 80-150 rpm.

5. The process according to any one of claims 1 to 4, wherein in step 2), the low-temperature filtration is carried out at a temperature of from-20 ℃ to 10 ℃, preferably from-20 ℃ to 0 ℃, and a filtration pressure of from 0.2MPa to 0.4MPa (gauge pressure), preferably from 0.2MPa to 0.3MPa (gauge pressure).

6. The method according to any one of claims 1 to 5, wherein in step 2), the reducing agent is selected from at least one of metal powder, potassium iodide, sulfite, and the like, preferably at least one of zinc powder, iron powder, and sulfite; the addition amount of the reducing agent is 1-2 wt% of the mass of the crude product.

7. The method according to any one of claims 1 to 6, wherein in step 3), the programmed cooling is performed at a cooling rate of 0.2 to 3 ℃/min, preferably in 3 stages, first at 0.2 to 0.5 ℃/min to 60 to 80 ℃, then at 1 to 3 ℃/min to 30 to 40 ℃, and finally at 0.2 to 0.3 ℃/min to-20 to 10 ℃.

8. The method according to any one of claims 1 to 7, wherein in step 3), the incubation recrystallization time is 2 to 8 hours, preferably 4 to 6 hours;

in the cooling and recrystallization processes, the stirring speed is 30-200 rpm, preferably 50-80 rpm.

9. The process according to any one of claims 1 to 8, wherein in step 3), the low-temperature filtration is carried out at a temperature of from-20 ℃ to 10 ℃, preferably from-10 ℃ to 0 ℃, and a filtration pressure of from 0.1 MPa to 0.5MPa (gauge pressure), preferably from 0.2MPa to 0.3MPa (gauge pressure).

10. The method of any of claims 1-9, wherein in step 1), the method for preparing an aromatic diimide is reacting a dialkali metal salt of a dihydroxy aromatic compound with a reactive substituted phthalimide;

the product mixture comprises a dialkali metal salt of a dihydroxy aromatic compound, a corresponding dihydroxy aromatic compound, at least one of the corresponding monosubstituted salts of the dihydroxy aromatic compound, or a combination comprising at least one of the foregoing, and an aromatic diimide.